The overall goal of this project is to understand the spatial and temporal relationship of cortical field potentials (fp) and their relationship to patterns of action potential (ap) activity in the normal brain. The knowledge gained will be used to develop neurotechnologies to improve understanding of brain disorders and to generate more effective neural interface systems for control and independence in individuals suffering from neurological injury and disease. Long-term simultaneous recording of both fps and aps from large numbers of neurons in the central nervous system is one of the key techniques used by neural prosthesis researchers to collect neuronal signals for prosthetic control. Neurophysiologists also utilize the technique for studying neuronal interactions, plasticity, and learning. In moving towards the long-term goal of developing an integrated microelectrode system that permits recording of extracellular neural activity from many neurons over decades of use in human neuroprostheses, this project will build on previous results with an emphasis on chronic implant applications. Specifically, this project will focus on chronic applications comparing subcompact subdural electrocorticography grids (EcoG) with multielectrode intracortical arrays in non-human primates with the goal of eventually developing a system capable of providing chronic neural recordings from human cortex. The focus will be on (1) understanding the nature of cortical fps at various frequency bands, (2) the relationship of fp band signals to underlying aps, and (3) the long term reliability, safety, and effectiveness of the devices. As such, there are three specific aims of this project: 1) Define the relationship between specific frequency bands in the EcoG field potentials in the perirolandic arm area cortex and arm movement. 2) Define the relationship between specific frequency bands in the EcoG field potentials and intracortical neuronal action potential spiking patterns in the perirolandic arm area cortex. 3) Study the long-term reliability and biocompatibility of chronically implanted subcompact EcoG vs. silicon- based electrode arrays, develop methods and materials to maximize their reliability and potential for motor neuroprosthesis application.